
where \(\widetilde{A}\in \mathbb {R}^{({{n}{-}1})\times {b}}\)  is a reduced incidence matrix, i.e., \(A\)  with one row removed, and
\(\eta \)  denotes the \(({n}-1)\) -dimensional vector of node potentials.
By [1]} \(\widetilde{A}_\texttt {T}\)  is nonsingular, and
\( F &= -(\widetilde{A}_\texttt {T}^{-1} \widetilde{A}_{\texttt {T}^*})^ \quad \text{independent of which row was removed}.\) 
